UltraISO - CD image files are easily created with UltraISO.
Restic - Easy: Doing backups should be a frictionless process, otherwise you are tempted to skip it.
PowerISO - PowerISO is a virtual drive that allows users to encode, burn, mount, and even encrypt CDs, DVDs, and BDs. The software can be downloaded from many platforms and sites online.
Duplicati - Free backup software to store backups online with strong encryption. Works with FTP, SSH, WebDAV, OneDrive, Amazon S3, Google Drive and many others.
WinCDEmu - WinCDEmu is an open-source CD/DVD/BD emulator.
rsync - rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync.